In Situ Hydrogen Activation Inspiring Efficient One-Pot Hydrogenation of Halogenated Nitrobenzenes over Ni–Co-Based Composites

Abstract

Selective hydrogenation of halogenated nitrobenzenes (XNBs) to halogenated amines (XANs) is of great importance for practical applications. Non-noble metal-based catalysts have shown prominent advantages in price and reserves accompanying low activity and selectivity toward the hydrogenation of halogenated nitrobenzenes (XNBs) even under harsh conditions. In this work, inexpensive Ni–Co-based composites (NxCC) were prepared for in situ tandem hydrogenation of XNBs to XANs by using hydrogen released from ammonia borane (AB) hydrolysis under ambient pressure. The results show these NxCC samples exhibited superior catalytic performance against Co3O4 or NiO samples. A selected N0.2CC catalyst as the mainly screened one can quantitatively convert XNBs to XANs with unprecedented activity with 100% XAN conversion. This catalyst can completely convert m-chloronitrobenzene (m-CNB) to m-chloroaniline (m-CAN), suggesting N0.2CC efficiently suppresses the further dichlorination of m-CAN. Recycling test shows the N0.2CC possesses higher stability and recyclability. The N0.2CC catalyst was found to be a dual catalyst that synergistically catalyzes both the AB dehydrogenation (about 1735 mL min–1 g–1 of hydrogen generation rate) and the subsequent hydrogenation (almost 100% conversion) of XNBs. Notably, it is the first time that the rapid in situ hydrogen activation (IHA) which facilely arouses the efficient hydrogenation of adsorbed substrate on the surface of catalyst has been elaborated. From a unique perspective, distinctive and simple control experiments were innovatively designed for testifying the advantage of tandem hydrogenation in contrast with traditional hydrogenation. This work presents an efficient and environmental strategy to selectively produce XANs from XNBs using high-performance non-noble metal composites.

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